The present invention relates generally to airplane landing gear assemblies, and more particularly to main landing gear assemblies for large commercial jet airplanes.
Large commercial jet airplanes typically include two main landing gear assemblies swingably attached to the undersides of the wings near the fuselage. Such landing gear assemblies are swung downwardly for taxiing and landing of the airplane and are retracted during flight by swinging them inwardly and upwardly into retracted positions wherein the landing wheels are stowed in wheel bays in the airplane fuselage.
Such landing gear assemblies are subject to several types of mechanical load during normal operations. When the airplane is stationary or slowly taxiing, the landing gear assemblies must be capable primarily of withstanding the static weight load of the airplane. During landing of the airplane, the main landing gear assemblies are additionally subjected to large, rearwardly directed drag loads as the airplane touches down on the runway and the brakes are applied. Also, the gear must withstand side loads which are generated during steering maneuvers. All of these various loading conditions are reacted by the gear components and, ultimately, by the gear support structures which attach the gear to the airplane. Ongoing developmental efforts have been directed toward providing a landing gear assembly and support structures that can accommodate both the static and dynamic loads with a minimum of size and weight.
A prime object of these efforts has been to alter and simplify the load path geometry of the gear so as to reduce loads in the individual gear components and to redirect loads from the gear to more substantial parts of the airplane, such as into the body, rather than into the wing spar or the landing gear support beam. It is also recognized that such a distribution of loads would permit some reduction to be made in the overall net weight of the airplane.
It has also been a major object of recent developmental efforts to increase the lateral distance (track width) between landing gear assemblies and also move the gear rearward on the airplane. Increasing the track width is desirable for the purpose of improving the stability of the airplane on the ground; however, its main purpose here is to improve the flotation characteristics of the airplane in order to meet certain weight load regulations being promulgated at LaGuardia Airport, New York.
Moving the landing gear assemblies further aft on the airplane is desirable for the purposes of accommodating a rearwardly displaced center of gravity and a low or up-balancing tail load. Moving the landing gear aft under such conditions results in increased lift and lowered drag for the airplane during flight. It also results in a possible weight reduction in the aft body of the airplane.
Previous proposals to increase the track width and also move the landing gear aft have proven unacceptable for several reasons. Briefly, such proposals have generally required increased gear and attendant complexity of mechanical attachments, have involved increased load path complexity and risk, and have required excessive angularity with respect to the vertical of the main oleo motion. Also, the previous proposals have been recognized as carrying an increased potential for wing fuel tank rupture in the event of landing gear collapse or have been based on unproven departures from accepted design practice.
Accordingly, it is an object of the present invention to provide a main landing gear assembly for a large commercial airplane wherein weight, side and drag loads on the main landing gear shock strut are distributed to fixed points on the fuselage body in addition to the points of attachment of the landing gear trunnion on the wing.
It is also an object of the present invention to provide a main landing gear assembly for a large commercial airplane that provides a greater track width and improved stability to the airplane, and wherein the landing wheels may be positioned further aft than has heretofore been possible.
It is another object of the present invention to enable a reduction to be made in the overall airplane weight by distributing loads on the landing gear to a greater number of fixed points on the fuselage body.
It is yet another object of the present invention to attain the foregoing objects using a minimum of additional mechanical components employed in accordance with proven design practices. Also, it is an object to provide a main landing gear assembly wherein the main shock strut and landing wheels swing in a controlled manner during retraction and extension such that the landing gear assembly may be reliably deployed in a free-fall extension during an emergency situation involving a power outage.
It is yet another object of the present invention to provide a landing gear assembly that is of decreased potential for wing fuel tank rupture in the event of a landing gear collapse.